Interpretive Summary: Development of high yielding wheat (Triticum aestivum L.) varieties with acceptable end-use quality is a major focus in breeding programs worldwide. Variations in molecular size of wheat endosperm proteins are known to influence end-use quality traits. In this paper, we report the relationship of grain yield with molecular size distribution of wheat endosperm proteins analyzed by the size-exclusion high performance liquid chromatography (SE-HPLC). Two individual protein fractions that were extractable and unextractable in sodium-dodecyl sulfate (SDS) buffer solution were analyzed for size distribution using the SE-HPLC protocol. Individual protein fractions had different associations with grain yield according to solubility in SDS buffer solution and molecule size. SDS-extractable fractions rich in polymeric proteins with small molecule size had a negative correlation (r = -0.41) with grain yield indicating that some of the high yielding lines had low content of those protein fractions in wheat samples. The SDS-unextractable fractions that were rich in very large polymeric proteins did not show any significant association with grain yield. There have been efforts to increase total protein content in wheat breeding for improvement of breadmaking quality. However, decrease in grain yield has been pointed out as a problem in breeding for high protein content. Since the large polymeric proteins in SDS unextractable fraction were not related to variation in grain yield, the protein fractions identified in this research are most likely useful in segregating wheat lines to improve breadmaking quality maintaining high grain yield.

Technical Abstract:
Development of high yielding wheat (Triticum aestivum L.) varieties with acceptable end-use quality is a major focus in breeding programs worldwide. Variations in molecular weight (Mw) distribution of endosperm proteins are known to influence end-use quality traits. This paper reports the relationship of the size-exclusion high performance liquid chromatography (SE-HPLC) profile of endosperm proteins with grain yield. Flour samples were previously analyzed for Mw distribution of sodium-dodecyl sulfate (SDS) buffer extractable and unextractable proteins using the SE-HPLC protocol. Correlations were calculated between grain yield and HPLC absorbance data obtained at 0.01-min retention time intervals. Although both SDS-extractable and unextractable proteins had positive correlations with grain protein content, only SDS-unextractable very high Mw polymeric proteins (UVHP) had no negative association with grain yield, while SDS-extractable fractions rich in low Mw polymeric proteins had a negative correlation (r = -0.41) with grain yield. These results suggest that in an effort to increase grain yield, breeding programs should target grain yield and also increase levels of UVHP and decrease SDS extractable polymeric proteins, thereby, maintaining acceptable bread-making quality.